Electrical Switches of the so-called universal fuse-switch type are marketed by the assignee of the instant invention under the designations UFS 1 and UFS 2.
One problem involved in such switches which requires improvement is to ensure the isolation of bursts of ionized gas that are typically generated upon breakage of the circuits corresponding to the respective phases of the AC mains supply. Isolation must be effected in such a manner that arcing does not occur between the respective phases of the supply as a result of the presence of the ionized gases that may provide a path of reduced resistance through the air dielectric between adjacent terminals or switch contacts of the respective phases.
Another aspect of such switches that is susceptible of improvement involves the manual actuating mechanism. Switches of the kind referred to above are actuated by means of a rotary spindle and the actuating mechanism incorporates two degrees of lost motion, firstly between the moving contacts of the switch and an over-center spring mechanism for providing snap-actuation of the switch during opening and closing of the switch contacts and secondly, between the manual actuating spindle and the over center spring mechanism, in order to prevent the over center spring mechanism from being held manually against the action of the over center spring. In order that the position of the actuating spindle in the idle condition of the switch should accurately reflect the open or closed condition of the switch, it is desirable that the actuating spindle should be reliably spring loaded into a rest position that is constant with respect to its range of lost motion. In hitherto known switches of the type referred to, frictional forces on the operating spindle tend to allow the latter to occupy a rest position that is displaced from the intended position, so that the position of the manual actuating member does not always clearly correspond to the appropriate rest condition of the switch.